Internal combustion engines drive pistons using a mixture of fuel and combustion air. The operation of the engine's combustion cylinders and the regulation of air flow in the intake apparatus of the engine can create pumping losses in certain circumstances. Such pumping losses can degrade engine performance and reduce fuel economy. Pumping loss in internal combustion engines is the power required to perform intake pumping during charge intake. During the intake stroke, the pressure acting on top of the piston is intake manifold pressure, minus whatever pressure losses occur as the intake charge passes through the intake port and valve.